10 February 2009

Overfishing on coral reefs: some factors

Overfishing isn't simply caused by too many people. A recent study has found that the biomass of fish found on coral reefs in the western Indian Ocean depended mostly on the complexity of the reefs themselves and the socioeconomic status of the people living on the shores.

In moderately developed places, people tend to depend less on fishing, they also have more access to engine-powered boats, spear guns, and other technologies that can rapidly deplete some fish species. Those locations also tended to have fewer traditional village rules to limit fishing and national governments that are too weak to effectively enforce fishery regulations.Rise Or Fall Of Reef Fish Driven By Both Economy And EcologyScienceDaily 9 Feb 09;

Overfishing on coral reefs isn't simply caused by too many people, according to a new report published in the February 10th issue of Current Biology, a Cell Press publication. Rather, the researchers found that the biomass of fish found on coral reefs in the western Indian Ocean depended mostly on the complexity of the reefs themselves and the socioeconomic status of the people living on the shores.

Specifically, they found, overfishing is at its worst in areas that have climbed only part way up the development ladder. In such locations, fish numbers were only one quarter what they were in places with either higher or lower levels of development.

Moderately developed places often had a few amenities, such as roads, schools, and electricity, but were generally considered poor by global standards, said Joshua Cinner of James Cook University in Australia. While people there tend to depend less on fishing, they also have more access to engine-powered boats, spear guns, and other technologies that can rapidly deplete some fish species. Those locations also tended to have fewer traditional village rules to limit fishing and national governments that are too weak to effectively enforce fishery regulations.

"In short, they have the technology to plunder their reefs, but not the institutions to protect them or the levels of development that allow for sufficient alternatives to fishing," Cinner said.

The findings suggest that the sustainability of coral reefs will depend in large part on whether developing countries can improve their well-being without falling into a poverty trap, he added. A poverty trap occurs when communities are forced to degrade the very resources they rely on due to a lack of alternatives for making ends meet.

"Those conditions can create a cycle of poverty and resource degradation, and the danger is that, if pushed too hard, reefs may lose their ability to bounce back when and if economic conditions improve," Cinner said. "For communities already in a poverty trap, governments and donors need to help them get out and couple this development with good governance and strong institutions."

Cinner noted that the current economic crisis can actually offer a "window of opportunity" for western governments, non-governmental organizations (NGOs), and donors to restructure aid and conservation efforts to better tackle root causes of reef decline. While some coral reef conservation projects already do try to consider socioeconomic issues and provide people with alternatives to fishing, the new findings suggest that those efforts likely won't be enough, he added. "Reef fisheries don't seem to get better until very substantial improvements in human welfare have been made," he said.

The bottom line, he says: "While there are certainly some real challenges facing reefs, the path to their destruction is not inevitable. They can be sustained with the right combination of approaches, which includes promoting strategies such as fishery closures while at the same time tackling poverty as a root cause of the degradation of reefs and their fish stocks."

The researchers include Joshua E. Cinner, Australian Research Council Centre of Excellence for Coral, James Cook University, Townsville, Australia; Timothy R. McClanahan, Wildlife Conservation Society, Marine Program, Bronx, NY; Tim M. Daw, University of East Anglia, Norwich, UK; Nicholas A.J. Graham, Australian Research Council Centre of Excellence for Coral, James Cook University, Townsville, Australia; Joseph Maina, Wildlife Conservation Society, Marine Program, Bronx, NY; Shaun K. Wilson, Australian Research Council Centre of Excellence for Coral, James Cook University, Townsville, Australia; and Terence P. Hughes, Australian Research Council Centre of Excellence for Coral, James Cook University, Townsville, Australia.

Wealthy areas and least developed regions have healthiest fish populations, while those in the middle are suffering

The economy isn't just squeezing the middle class on land, it's also affecting fish.

According to a study by the Wildlife Conservation Society (WCS) and other organizations, researchers discovered a surprising correlation between "middle class" communities in Eastern Africa and low fish levels. Curiously, areas with both low and high socio-economic levels had comparatively higher fish levels.

Appearing in the latest edition of Current Biology, the study examined reef systems, human population densities, and socio-economics among villages in 30 fished and unfished study sites in five countries along Africa's Indian Ocean coast.

The study is by Josh Cinner of James Cook University (JCU), Tim McClanahan of the Wildlife Conservation Society (WCS), Tim Daw of the University of East Anglia, Nick Graham of JCU, Joseph Maina of WCS, and Shaun Wilson and Terry Hughes of JCU.

In a comparison between villages, researchers found that communities with intermediate levels of infrastructure had the lowest fish levels in their adjacent reef systems—up to four times lower than sites of low and high levels of development.

"This is a significant finding on how socio-economics can influence reef fisheries in surprising ways," said Dr. Tim McClanahan, a WCS coral researcher and co-author of the study. "It also shows the importance of combining ecology with social science for conservation planning on a regional scale."

The explanation, said researchers, lies in the interplay between traditional customs and how growth influences the social fabric of communities. In poor communities, many of which rely heavily on marine resources, fishing levels are kept in check by local cultural institutions and taboos and a reliance on traditional, low-tech fishing methods. Increases in wealth often reduce a community's dependence on fishing, but it can also increase the number of motorized fishing vessels and fishing gear such as handlines.

Economic growth during the early stages can also erode cultural restrictions on overfishing, according to the authors. The net result: fewer fish. Among the countries studied, Kenya in particular, has experienced a sharp decline in cultural restraints and a subsequent increase in unrestrained and destructive fishing techniques.

The most affluent communities, by contrast, become less dependent on marine resources and more diversified economically, with more salaried positions and economic opportunities. Wealthier communities also possess higher levels of technology—larger boats that enable fishermen to fish on the open sea—and an increased awareness on the importance of coral reefs on ecological health.

The U-shaped curve in fish biomass with respect to socioeconomic levels approximates what is known as an environmental "Kuznet curve," which is adapted from a graphical model that measures economic inequalities in developing countries driven by the extent of a countries economic influence.

Predictably, the research also found that fish levels were always negatively but not strongly affected by high human population density. And protected marine sites with no fishing had fish levels three times higher than sites where fishing was permitted.

"Coral reef fishery management will depend not just on fishing laws but also on improving human welfare and institutional capacity through appropriate socioeconomic development" added McClanahan. "Governments, donors, and other agencies help communities avoid 'poverty traps' through investments in programs and alternatives to reef-based livelihoods, where obvious examples include infrastructure developments such as schools and hospitals."

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